Method for lining a pipe or main

ABSTRACT

A method for lining a pipe or main comprising heating a length of synthetic-resin liner pipe 20 of external diameter substantially equal to or greater than the internal diameter of the pipe or main 40 to be lined, mechanically deforming the heated liner pipe 20 to reduce its external diameter to less than the internal diameter of the pipe or main 40 to be lined, causing the liner pipe 20 to enter the pipe or main 40 to be lined and pressurizing the internal wall of the liner pipe 20 to cause it to expand into engagement with the internal wall of the pipe or main 40 to be lined.

.Iadd.This application is a Continuation of application Ser. No.08/603,199, filed on Feb. 20, 1996 (now abandoned) which is a FileWrapper Continuation of application Ser. No. 08/028,609, filed on Mar.08, 1993 (now abandoned) which is a File Wrapper Continuation ofapplication Ser. No. 07/683,494, filed on Apr. 10, 1991 (now abandoned)which is a File Wrapper Continuation of application Ser. No. 07/401,925,filed on Sep. 01, 1989 (now abandoned) which is a Reissue of applicationSer. No. 07/013,034, filed Feb. 10, 1987, now U.S. Pat. No. 4,777,984granted on Oct. 18, 1988..Iaddend.

FIELD OF THE INVENTION

The present invention relates to a method for lining a pipe or main andis particularly directed to the lining of underground gas or water mainsor sewer pipes.

BACKGROUND OF THE INVENTION

According to one aspect of the present invention, we provide a methodfor lining a pipe or main comprising heating a length of synthetic-resinliner pipe of external diameter substantially equal to or greater thanthe internal diameter of the pipe or main to be lined, mechanicallydeforming the heated liner pipe to reduce its external diameter to lessthan the internal diameter of the pipe or main to be lined, causing theliner pipe to enter the pipe or main to be lined and pressurising theinternal wall of the liner pipe to cause it to expand into engagementwith the internal wall of the pipe or main to be lined.

According to another aspect of the present invention, a closure isprovided for closing off the end of a synthetic resin liner pipe duringinternal pressurisation of the pipe with a pressurising fluid, theclosure comprising a cap having a sleeve portion adapted to receive theend of the pipe with clearance and flexible sealing means located withinthe sleeve and adapted to engage the outer surface of the pipe and forma seal between the outer surface of the pipe and the inner surface ofthe sleeve portion.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be particularlydescribed with reference to the drawings in which:

FIG. 1 is a plan view of a rig suitable to preheat and reduce theexternal diameter of a length of liner pipe,

FIG. 2 is a more detailed cross-section of the front end of the rig inuse,

FIGS. 3 to 9 show in schematic form a typical sequence of operations inthe lining of a section of an existing main and

FIGS. 10 and 11 are longitudinal sections through one form of device forclosing the ends of the liner pipe so that it can be expanded bypressurisation, FIG. 10 showing the situation before expansion and FIG.11 the situation after expansion.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring to FIG. 1, a rig 1 comprises a heater tube 2 which in use issupported above ground on a support frame 3 (see also FIGS. 5 and 6).The tube 2 has a rear end 4 to receive a liner pipe for preheating onpassage through the tube 2 and a front end 5 adapted to reduce theexternal diameter of the preheated liner pipe.

Extending parallel to the heater tube 2 is a smaller diameter tube 6serving to provide hot gas for preheating a liner pipe within the heatertube 2.

The tube 6 is closed at a rear end 7 by an apertured plate 8 through theaperture of which extends a gas supply pipe 9 for supplying gas to a gasfired burner 10 located within the tube 6. The tube 6 is provided withan air-intake 11 at a point adjacent to the plate 8 to supply air forcombustion of the gas within the burner 10.

Hot gas supplied by the burner 10 travels forwardly in the direction ofthe arrows to an elongated chamber 12 forming the front end of the tube6. The chamber 12 terminates in a distributor 13 which has a rectangularoutlet 14 communicating with a similarly shaped rectangular slot in thewall of the heater tube 2. In this way the hot gas is caused to enterthe heater tube 2 from the chamber 12 radially at a point adjacent tothe front end 5 of the heater tube 2 taking the direction of the arrows.Once inside the tube 2, the gas travels rearwardly in the direction ofthe arrows.

Some of the hot gas then leaves the tube 2 by way of an exhaust pipe 15located adjacent to the rear end 4 of the tube 2. The remaining majorityof the hot gas re-enters the tube 6 by way of a radial tube 16connecting the tubes 2 and 6 at a point adjacent to their rear ends.

The chamber 12 is provided with a circulating fan 17 to cause thecirculation of the gas within the assembly to be accelerated.

Referring to FIGS. 1 and 2 the front ends of the tube 2 is formed by twoswaging dies 18 and 19 serving in use to reduce the external diameter ofa liner pipe 20 being drawn therethrough.

The first die 18 is located within the tube 2 and is held within a dieholder 21 secured to the internal wall of the tube 2. The first die 18has a forwardly tapering entry section 22 leading to a circular exitsection 23. The tapering entry section 22 serves to provide the initialand major proportion of the reduction in the external diameter of thepreheated liner pipe 20 as shown in FIG. 2.

The second die 19 is located beyond the end of the tube 2 and is boltedto a circular flange 24 welded to the outer surface of the tube 2. Thesecond die has a forwardly tapering aperture 25 serving to provide afinal and minor proportion of the reduction in the external diameter ofthe preheated liner pipe 20.

In use, the preheated liner pipe 20 is drawn sequentially through thedies 18 and 19 by means of a cable 26 of a winch 48 (shown in FIG. 4).To achieve this, the leading end of the liner pipe 20 is formed in theshape of a cone 28 by cutting the end of the liner pipe 20 into suitablytriangular portions 29, folding the portions 29 to form the cone 28 andthen welding adjacent portions 29 together. The portions 29 are formedwith holes to receive the ends of bolts 30, and gaps 31 are left betweenthe portions 29 so that, when the cone 28 has been formed, the inside ofthe cone 28 can be accessed manually to place nuts 32 on the ends of thebolts 30. Next a steel cone 33 matching the tip of the pipe cone 28 isplaced over the tip of the cone 28 as shown in FIG. 2, the steel cone 33having holes to correspond with those in the pipe cone 28, and the cones28 and 33 are bolted together by the nuts and bolts 32 and 30.

The steel cone 33 has an eye 34 which is in use as shown in FIG. 2connected to the cable 26 of the winch 48.

The internal diameter of the wall of tube 2 is greater than the externaldiameter of the liner pipe 20 so that an annular space 35 is formedbetween the outer wall of the liner pipe 20 and the inner wall of thetube 2. In use, the space 35 when the liner pipe 20 is within the tube 2is enclosed at one end by the internal die 18 and at the other end by aplate 36 having an aperture 37 and being attached to the rear end 4 ofthe tube 2, the wall of the aperture 37 in the plate 36 forming a closefit with the external wall of the liner pipe 20. Thus, the hot gasentering the tube 2 from the distributor 13 is caused to flow within theenclosed annular space 35 to heat the external wall of the liner pipe20.

Referring to FIGS. 3 to 9, in the first stage of the lining process(FIG. 3), a section 40 of a main 41 to be lined has ends 42,43 isolatedfrom adjacent portions 44,45 of the main 41. This is done by diggingexcavations 46,47 at two distant points in the main 41 and then removingpieces from the main 41 to expose the ends 42,43 of the section 40.

In the next stage of the process (FIG. 4), a motorised winch 48 ismounted at ground level adjacent to the end 42 of the main section 40. Astiff rod 49 having an end 50 facing the winch 48 is then pushed alongthe main section 40 from the end 42 to the end 43. The end 50 of the rod49 is connected to the cable 26 after the cable 26 has been fed throughguide rolls 51 mounted on the floor of the excavation 46. The rod 49 isthen pushed completely through the section 40 so that the cable 26eventually emerges from the end 43 of the section 40.

The cable 26 is then detached from the rod 49 and is fed through the rig1 as shown in FIG. 5. The cable 26 is then attached to the leading endof the liner pipe 20 in the manner previously described with referenceto FIG. 2. Sections of the liner pipe 20 are fed successively to abutt-welding machine 60 located upstream of the rig 1. The machine 60enables adjoining ends of the pipe liner sections 20 to be butt weldedtogether to form a continuous length. The machine 60 may have facilitiesfor removing both internal and external weld beads from the liner pipe20 which ideally is of polyethylene.

In the next stage of the process (FIG. 6), the motor of the winch 48 isthen actuated to draw the cable 26 towards the end 43 of the section 40as shown in FIG. 6. This causes the liner pipe 20 to enter the heater 2through which hot gas is circulating. The liner pipe 20 is thenpreheated by the gas in the manner previously described to a temperatureof about 100° C., and the preheated liner pipe 20 is then drawn throughthe dies 18, 19 to effect a reduction in the external diameter of theliner pipe 20 (thereby erecting a reduced diameter pipe 61) to an extentpermitting the reduced diameter pipe 61 to enter the end 43 of thesection 40 by way of guide rolls 62 mounted on the floor of theexcavation 47.

The reduced diameter pipe 61 is then drawn as a continuous length alongthe section 40 to and out of the far end 42 as shown in FIG. 7. Thereduction in diameter of the liner pipe 20 may be of the order of 3% ormore.

Once the liner pipe 20 has reached and extended beyond the far end 42 ofthe section 40, the cable 26 is disconnected from the eye 34 on thesteel cone 33. The steel cone 33 is then removed from the pipe cone 28,thus leaving the liner pipe 20 with ends 62a and 63 lying exposed beyondthe ends 42,43 of the section 40. Both ends of the liner pipe 20 areclosed by closures 64, and air is injected into one end of the linerpipe 20 by means of a compressor 65 mounted at ground level adjacent tothe end 63 of the main section 40 as shown in FIG. 8. The air isinjected at super atmospheric pressure (e.g., 2 to 6 bar) for anextended period (say 24 hours). This causes the liner pipe 20 to expandinto contact with the internal wall of the section 40 as shown in FIG.9.

A suitable closure 64 for the liner pipe 20 is shown in FIGS. 10 and 11.The closure 64 comprises a tubular sleeve 66 for receiving one end ofthe liner pipe 20 and a cap 67 for attachment to the sleeve 66.

The cap 67 has a cylindrical portion 68 having an outwardly flanged openend 69 for connection to a similar outwardly flanged end 70 on thesleeve 66 by means of several nut and bolt assemblies 71 (only twoshown). The cap 67 has one end closed by a plate 72 which has a valve 73which is adapted when open to connect the interior of the closure 64 tothe compressor 65 or like device for supplying air under pressure to theclosure 64. Alternatively, the valve 73 can be closed when the closure64 is serving as a seal for preventing the escape of air from one end ofthe liner pipe 20 when air is being injected at the other end.

Located in two circumferential grooves 74 on the inner surface 75 of thesleeve 66 are two O-ring seals 76 which are arranged to engage the outersurface 77 of the liner pipe 20 when an end of the liner pipe 20 islocated within the sleeve 66. The seals 76 form a seal between the outersurface 77 of the liner pipe 20 and the inner surface 75 of the sleeve66 and permit movement of the liner pipe 20 within the sleeve 66 sincethe liner pipe 20 expands radially and contracts longitudinally aspressure is applied to the interior of the liner pipe 20.

In use, both the exposed ends of the liner pipe 20 are closed with aclosure device 64. The sleeve 66 may have a recessed end portion 78 tofit over the corresponding end 42, 43 of the main section 40 as shown inFIGS. 10 and 11. Each closure 64 is supported against the internal wallsof the excavation by means of struts 79 extending outwardly from the cap67 to prevent its being blown off during pressurisation of the closure64. One of the closure devices 64 is connected to the compressor 65 bymeans of the valve 73, which is opened. The valve 73 of the otherclosure 64 is closed. Air is then supplied by the compressor 65 topressurise the liner pipe 20. After use, the closures 64 are removed,and the ends of the liner pipe 20 are connected up to the adjacentportions 44 and 45 of the main 41 by conventional means.

The pressurisation of the liner pipe may form part of a standardpressure test to test the soundness of the liner pipe 20.

I claim: .[.1. A method of lining an underground pipe or main, saidmethod comprising the steps of: of a cable attached to the leading edgeof the liner pipe..]..[.6. A method as claimed in claim 5 in which thecable is wound onto the drum of a motorized winch to draw the liner pipeinto the underground pipe or main to be lined..]..[.7. A method asclaimed in claim 1 in which a succession of lengths of synthetic-resinpipe are butt-welded together to obtain the liner pipe..]..[.8. A methodas claimed in claim 1 in which the internal wall of the liner pipe ispressurized at superatmospheric pressure..]..[.9. A method as claimed inclaim 8 in which the internal wall of the liner pipe is pressurized withair..]..[.10. A method as claimed in claim 1 in which both ends of theliner pipe are closed with closures to enable the internal wall of theliner pipe to be pressurized..]..[.11. A method as claimed in claim 1 inwhich the synthetic-resin is polyethylene..]..Iadd.12. A method oflining an underground pipe or underground main, said method comprisingthe steps of:(a) preheating a continuous length of synthetic-resin linerpipe of external diameter substantially equal to or greater than theinternal diameter of the underground pipe or underground main to belined to a temperature of about 100° C.; (b) drawing the so-heatedcontinuous length of liner pipe into the underground pipe or undergroundmain to be lined through at least one swaging die dimensioned to reducethe external diameter of the continuous length of liner pipe to lessthan the internal diameter of the underground pipe or underground mainto be lined; (c) reducing the external diameter of the continuous lengthof liner pipe to less than the internal diameter of the underground pipeor underground main to be lined; and (d) pressurizing the internal wallof the continuous length of liner pipe with air at superatmosphericpressure to cause it to expand into engagement with the internal wall ofthe underground pipe or underground main to be lined..Iaddend..Iadd.13.A method of lining an underground pipe or underground main, said methodcomprising the steps of:(a) preheating a continuous length ofsynthetic-resin liner pipe of external diameter substantially equal toor greater than the internal diameter of the underground pipe orunderground main to be lined; (b) drawing the so-heated continuouslength of liner pipe into the underground pipe or underground main to belined through at least one swaging die dimensioned to reduce theexternal diameter of the continuous length of liner pipe to less thanthe internal diameter of the underground pipe or underground main to belined; (c) reducing the external diameter of the continuous length ofliner pipe on the order of about 3% to about 10% less than the internaldiameter of the underground pipe or underground main to be lined; and(d) pressurizing the internal wall of the continuous length of linerpipe with air at superatmospheric pressure to cause it to expand intoengagement with the internal wall of the underground main to belined..Iaddend..Iadd.14. A method of lining an underground pipe orunderground main, said method comprising the steps of: (a) preheating acontinuous length of synethetic-resin liner pipe of external diametersubstantially equal to or greater than the internal diameter of theunderground pipe or underground main to be lined; (b) drawing theso-heated continuous length of liner pipe into the underground pipe orunderground main to be lined through at least one swaging diedimensioned to reduce the external diameter of the continuous length ofliner pipe to less than the internal diameter of the underground pipe orunderground main to be lined; (c) reducing the external diameter of thecontinuous length of liner pipe to less than the internal diameter ofthe underground pipe or underground main to be lined; and (d)pressurizing the internal wall of the continuous length of liner pipewith air at superatmospheric pressure of about 2 bar to about 6 bar tocause it to expand into engagement with the internal wall of theunderground pipe or underground main to be lined..Iaddend..Iadd.15. Amethod as claimed in claim 12 wherein;the step of reducing the externaldiameter of the continuous length of liner pipe comprises reducing saiddiameter on the order of about 3% to about 10%..Iaddend..Iadd.16. Amethod as claimed in claim 12 wherein; the step of pressurizing theinternal wall of the continuous length of liner pipe is carried out at apressure of about 2 bar to about 6 bar..Iaddend..Iadd.17. A method asclaimed in claim 13 wherein; the step of pressurizing the internal wallof the continuous length of liner pipe is carried out at a pressure ofabout 2 bar to about 6 bar..Iaddend..Iadd.18. A method as claimed inclaim 12 wherein;(a) the step of reducing the external diameter of thecontinuous length of liner pipe comprises reducing said externaldiameter on the order of about 3% to about 10%; and (b) the step ofpressurizing the internal wall of the continuous length of liner pipe iscarried out at a pressure of about 2 bar to about 6bar..Iaddend..Iadd.19. A method of lining an underground pipe orunderground main, said method comprising the steps of:(a) preheating acontinuous length of synthetic-resin liner pipe of external diametersubstantially equal to or greater than the internal diameter of theunderground pipe or underground main to be lined; (b) drawing theso-heated continuous length of liner pipe into the underground pipe orunderground main to be lined through at least one swaging die, which isabove ground and out of axial alignment with the underground pipe orunderground main to be lined, said die being dimensioned to reduce theexternal diameter of the continuous length of liner pipe to less thanthe internal diameter of the underground pipe or underground main to belined; (c) reducing the external diameter of the continuous length ofliner pipe to less than the internal diameter of the underground pipe orunderground main to be lined; and (d) pressurizing the internal wall ofthe continuous length of liner pipe with air at superatmosphericpressure to cause it to expand into engagement with the internal wall ofthe underground pipe or underground main to be lined..Iaddend..Iadd.20.A method as claimed in claim 19 in which the continuous length of linerpipe is preheated by means of a portable heatingdevice..Iaddend..Iadd.21. A method as claimed in claim 20 in which theportable heating device comprises a heating chamber through which, inuse, the continuous length of liner pipe is drawn..Iaddend..Iadd.22. Amethod as claimed in claim 21 in which the heating chamber includes theat least one swaging die..Iaddend..Iadd.23. A method as claimed in claim19 in which the continuous length of liner pipe is drawn into theunderground pipe or underground main to be lined by means of a cableattached to the leading edge of the continuous length of linerpipe..Iaddend..Iadd.24. A method as claimed in claim 23 in which thecable is wound onto the drum of a motorized winch to draw the continuouslength of liner pipe into the underground pipe or underground main to belined..Iaddend..Iadd.25. A method as claimed in claim 19 in which asuccession of lengths of synthetic-resin pipe are butt-welded togetherto obtain the continuous length of liner pipe which is thenpreheated..Iaddend..Iadd.26. A method as claimed in claim 19 in whichboth ends of the continuous length of liner pipe are closed withclosures to enable the internal wall of the continuous length of linerpipe to be pressurized..Iaddend..Iadd.27. A method as claimed in claim19 in which the synthetic-resin is polyethylene..Iaddend.